In the past people have proposed blended wing body aircraft like the B-2 bomber and people have also proposed all flying Oblique Wings as shown in FIG. 1 with an elliptical or near elliptical planform.
Blended Wing Body aircraft like the B-2 achieve lower drag than a pure flying wing by minimizing the surface area exposed to the airflow. They do this by having a center body that is as close as practical to circular in planform but usually with a pointed nose on the front to reduce compressibility drag and with wings attached to the sides to increase the wingspan for reduced induced drag which is drag due to creating lift. A wing with a circular planform has the least amount of surface area to internal volume for the same reason that a circle has the smallest circumference to the enclosed area or a sphere has the largest volume to surface area. The Blended Wing Body aircraft also can have inherent pitch stability at a farther aft center of gravity due to the aft swept wings that can act like horizontal tail surfaces. Further background of blended wing body aircraft is given in R. H. Liebeck, “Design of the Blended-Wing-Body Subsonic Transport,” 2002 Wright Brothers Lecture, American Institute of Aeronautics and Astronautics, AIAA-2002-0002, reprinted in Journal Of Aircraft, Vol. 41, No. 1, January-February 2004, pp. 10-25, hereby incorporated by reference.
Oblique flying wing aircraft that have been proposed in the past were elliptical or near elliptical wings that flew at different oblique angles to trade off compressibility and induced drag at different mach numbers like that shown in planform in FIG. 1. The design shown in FIG. 1 has remained relatively unchanged since it was proposed by R. T. Jones in the 1950's. The history of oblique wing research is found in M. Hirschberg, D. Hart, and T. Beutner, “A Summary of a Half-Century of Oblique Wing Research,” 45th AIAA Aerospace Sciences Meeting and Exhibit, AIAA Paper 2007-150, January 2007, hereby incorporated by reference.
At low speed the aircraft could fly in a low speed direction 2 close to a zero sweep angle for minimum induced drag which is the drag due to lift. At high speed, compressibility drag becomes more important and eventually dominant. Compressibility drag due to lift and compressibility drag due to volume can however be reduced by spreading the lift and volume farther in the direction of flight. Thus as the aircraft flew faster and faster the wing was swept to a higher and higher sweep angle to trade off the optimum induced versus compressibility drag characteristics. The component of air velocity perpendicular to the wing could remain subsonic effectively making the wing and air interact very similar to a wing flying subsonically. Engines 6 were generally envisioned to be mounted in rotating pods on the bottom of the wing. The small chord length and limited thickness of the wing made integrating the engine into the wing more difficult and in order to have an aircraft with a thick enough wing that passengers could stand up in a cabin the aircraft had to be very large carrying approximately six hundred passengers. The largest circle possible 5 is shown drawn over (inscribed in) the planform of the aircraft shown in FIG. 1. As may be seen, it is a small circle encompassing only a small percentage of the planform area of the aircraft. From this we can determine that this aircraft has a large amount of surface area to internal volume ratio and as such will have a lot of skin friction drag in both high and low speed configurations. Also because the circle is small and there is a finite limit to the thickness to chord length of the airfoil used on this flying wing, we know the thickness of the vehicle will not be very large making packaging of the vehicle more difficult or requiring the vehicle to be larger than might be desirable such as to incorporate a cabin for passengers or other components.
In the past people have also proposed oblique wing aircraft that had conventional fuselages as well. Problems occurred due to the interaction between the wing and fuselage, and the high compressibility drag due to volume of the fuselage caused most designers to look to all-wing configurations.
Oblique flying wing aircraft have more surface area to volume than a Blended Wing Body aircraft like the B-2 stealth bomber and they also need the center of gravity very far forward or they are unstable and hard to control and generally have to be provided with an advanced artificial stabilization system.